rustdi 0.1.0

use crate::errors::*;
use crate::session_new::{Session, MultiDeviceSession, KeyPair};
use ring::{agreement, digest, hmac, hkdf, rand};
use std::sync::Arc;

#[derive(Debug)]
pub struct HandshakeMessage {
    pub client_hello: Option<ClientHello>,
    pub server_hello: Option<ServerHello>,
    pub client_finish: Option<ClientFinish>,
}

#[derive(Debug)]
pub struct ClientHello {
    pub ephemeral: Vec<u8>,
}

#[derive(Debug)]
pub struct ServerHello {
    pub ephemeral: Vec<u8>,
    pub static_key_encrypted: Vec<u8>,
    pub certificate_encrypted: Vec<u8>,
}

#[derive(Debug)]
pub struct ClientFinish {
    pub static_key_encrypted: Vec<u8>,
    pub payload_encrypted: Vec<u8>,
}

// Noise protocol untuk WhatsApp
pub struct NoiseHandler {
    ephemeral_key_pair: agreement::EphemeralPrivateKey,
    noise_key: Vec<u8>,
    static_public_key: Vec<u8>,
    static_private_key: Vec<u8>,
    handshake_state: HandshakeState,
}

#[derive(Debug, PartialEq)]
pub enum HandshakeState {
    Idle,
    ClientHelloSent,
    ServerHelloReceived,
    ClientFinishedSent,
    HandshakeComplete,
}

impl NoiseHandler {
    pub fn new() -> Result<Self> {
        let rng = rand::SystemRandom::new();
        
        // Generate ephemeral key pair
        let ephemeral_private_key = agreement::EphemeralPrivateKey::generate(&agreement::X25519, &rng)
            .map_err(|_| "Failed to generate ephemeral private key")?;
        
        let ephemeral_public_key = ephemeral_private_key.compute_public_key()
            .map_err(|_| "Failed to compute ephemeral public key")?;
        
        // Generate static key pair
        let static_private_key = agreement::EphemeralPrivateKey::generate(&agreement::X25519, &rng)
            .map_err(|_| "Failed to generate static private key")?;
        
        let static_public_key = static_private_key.compute_public_key()
            .map_err(|_| "Failed to compute static public key")?;

        Ok(NoiseHandler {
            ephemeral_key_pair: ephemeral_private_key,
            noise_key: vec![0; 32], // Diisi nanti
            static_public_key: static_public_key.as_ref().to_vec(),
            static_private_key: vec![], // Diisi nanti setelah diambil
            handshake_state: HandshakeState::Idle,
        })
    }

    pub fn start_handshake(&mut self) -> Result<Vec<u8>> {
        self.handshake_state = HandshakeState::ClientHelloSent;
        
        // Bangun pesan Client Hello
        let mut message = vec![0x01]; // Handshake type
        message.extend_from_slice(&self.ephemeral_key_pair.compute_public_key()
            .map_err(|_| "Failed to compute public key")?
            .as_ref());
        
        Ok(message)
    }

    pub fn process_server_hello(&mut self, server_hello: &ServerHello) -> Result<Vec<u8>> {
        if self.handshake_state != HandshakeState::ClientHelloSent {
            return Err("Invalid handshake state".into());
        }

        self.handshake_state = HandshakeState::ServerHelloReceived;

        // Proses kunci server
        // Ini adalah bagian penting dari protokol Noise
        let server_public_key = &server_hello.ephemeral[..32];
        let server_static_encrypted = &server_hello.static_key_encrypted;
        let certificate_encrypted = &server_hello.certificate_encrypted;

        // Compute shared secret dengan server ephemeral
        let server_public = agreement::UnparsedPublicKey::new(&agreement::X25519, server_public_key);
        let shared_secret = agreement::agree_ephemeral(
            self.ephemeral_key_pair.clone(),
            &server_public,
            |shared_secret| shared_secret.to_vec(),
        ).map_err(|_| "Failed to compute shared secret")?;

        // Ekstrak dan validasi sertifikat server
        let certificate = self.decrypt_noise_certificate(certificate_encrypted, &shared_secret)?;
        self.verify_server_certificate(&certificate)?;

        // Ekstrak kunci statis server
        let server_static_decrypted = self.decrypt_static_key(server_static_encrypted, &shared_secret)?;

        // Hitung kunci gabungan
        let combined_shared = self.calculate_combined_shared_secret(
            &shared_secret, 
            &server_static_decrypted
        )?;

        // Bangun pesan Client Finish
        let mut finish_message = vec![0x02]; // Client finish type
        finish_message.extend_from_slice(&self.static_public_key);
        
        // Enkrip payload (yang berisi token dll)
        let client_payload = self.build_client_payload();
        let payload_encrypted = self.encrypt_payload(&client_payload, &combined_shared)?;
        finish_message.extend_from_slice(&payload_encrypted);

        Ok(finish_message)
    }

    fn decrypt_noise_certificate(&self, encrypted_cert: &[u8], shared_secret: &[u8]) -> Result<Vec<u8>> {
        // Implementasi dekripsi sertifikat Noise
        // Dalam implementasi asli, ini akan menggunakan AES-GCM atau enkripsi lainnya
        Ok(encrypted_cert.to_vec()) // Placeholder
    }

    fn verify_server_certificate(&self, certificate: &[u8]) -> Result<()> {
        // Verifikasi sertifikat server
        // Ini adalah bagian penting dari keamanan protokol WhatsApp
        Ok(()) // Placeholder
    }

    fn decrypt_static_key(&self, encrypted_static: &[u8], shared_secret: &[u8]) -> Result<Vec<u8>> {
        // Dekripsi kunci statis dari server
        Ok(encrypted_static.to_vec()) // Placeholder
    }

    fn calculate_combined_shared_secret(&self, shared_secret: &[u8], server_static: &[u8]) -> Result<Vec<u8>> {
        // Gabungkan rahasia bersama untuk menghasilkan kunci akhir
        let combined = [shared_secret, server_static].concat();
        
        // Ekspansi rahasia menggunakan HKDF
        let salt = [0u8; 32]; // Salt nol seperti pada protokol WhatsApp
        let hkdf_salt = hkdf::Salt::new(hkdf::HKDF_SHA256, &salt);
        let pseudo_random_key = hkdf_salt.extract(&combined);
        
        let mut expanded = [0u8; 112]; // Ukuran yang digunakan WhatsApp
        pseudo_random_key.expand(&[], &mut expanded)
            .map_err(|_| "Gagal ekspansi rahasia")?;
        
        Ok(expanded.to_vec())
    }

    fn build_client_payload(&self) -> Vec<u8> {
        // Bangun payload klien (termasuk token klien/dll)
        vec![] // Placeholder
    }

    fn encrypt_payload(&self, payload: &[u8], combined_shared: &[u8]) -> Result<Vec<u8>> {
        // Enkripsi payload klien
        Ok(payload.to_vec()) // Placeholder
    }

    pub fn finalize_handshake(&mut self, shared_keys: &[u8]) -> Result<()> {
        if self.handshake_state != HandshakeState::ServerHelloReceived {
            return Err("Invalid handshake state for finalization".into());
        }

        // Simpan kunci yang dihasilkan
        if shared_keys.len() >= 64 {
            // Ambil kunci enkripsi dan HMAC dari hasil akhir
            let enc_key = &shared_keys[0..32];
            let mac_key = &shared_keys[32..64];
            
            // Update session dengan kunci baru
            self.noise_key.copy_from_slice(&enc_key);
        }

        self.handshake_state = HandshakeState::HandshakeComplete;
        Ok(())
    }

    pub fn encrypt_message(&self, message: &[u8]) -> Vec<u8> {
        // Enkripsi pesan menggunakan kunci noise
        message.to_vec() // Placeholder
    }

    pub fn decrypt_message(&self, encrypted_message: &[u8]) -> Result<Vec<u8>> {
        // Dekripsi pesan menggunakan kunci noise
        Ok(encrypted_message.to_vec()) // Placeholder
    }
}